The invention relates to an apparatus for forming stacks with print products, the apparatus comprising a platform on which the stacks are respectively formed and a lift for lifting up the print products.
Apparatuses of the aforementioned type have long been known in the print industry and, in particular, are configured as cross stackers which can be used to create stacks composed of layers that are rotated by 180° relative to each other. The stacks are created from print products such as newspapers, brochures, pamphlets, printed sheets and the like, for example by supplying the print products to the apparatus in an overlapping or shingled flow and with a suitable means of transportation. However, supplying the items individually is conceivable as well. The formed stacks are then removed with a suitable conveying means.
An apparatus of the aforementioned type is disclosed, for example, in European patent document EP 1 167 261 A. The print products supplied to the apparatus are deposited onto a vertically displaceable packing platform. A lift provided with a bottom press plate is disposed in the center of this packing platform. With the aid of the bottom press plate, a formed stack can be lifted up for compressing it and removing it by dropping the stack as a layer. The disadvantage of the known apparatus is that the bottom press plate must be replaced even for small changes in the print product format. It is therefore necessary to make available several such bottom press plates within a specified grid. A further difficulty with the known apparatus is that the folds on the print products are not compressed sufficiently during the compressing operation.
Another apparatus of the type first mentioned above is disclosed in European patent document EP 0 153 983 B, wherein this apparatus also comprises a lift with a base plate. For the compressing operation, compressing elements which can be pivoted are provided above the base plate, wherein a formed stack can be pressed against these elements by lifting up the base plate.
Finally, an apparatus for ejecting stacked printed sheets is disclosed in European patent document EP 0 829 441 A.